Adjustable inertial switch for a projectile



United States Patent Inventors Gerald L. llazelet Urbana; Donald A. Bednar, Champaign, Illinois Appl. No. 729,313 Filed May 15, 1968 Patented Sept. 22, 1970 Assignee The Magnavox Company Fort Wayne, Indiana a corporation of Delaware ADJUSTABLE INERTIAL SWITCH FOR A PROJECTILE 1 10 Claims, 7 Drawing Figs.

u.s. Cl 102/70.2

Int. Cl F42c 15/24, F42c 1 1/00, F42c 15/04 Field of Search 102/ 70.2

[56] References Cited UNITED STATES PATENTS 2,972,026 2/1961 Kendall 102/702 3,013,496 12/1961 Wenig lO2/70.2

Primary ExaminerBenjamin A. Borchelt Assistant ExaminerThomas H. Webb A ttomey Richard T. Seeger Sheet 1 of 2 FIIG.I

w A mmNN 0 A Y Bnwe 6 n 5m 5 L S v Rm 4 nwwcTt 5 0 MT 7 woe O GDJ 6 W 8 4 3 O G F Patented Sept. 22, 1970 3,529,549

Inveniors GERALD L. HAZELET DONALD ABEDNAR 7 \n JEFFERS Qouws ADJUSTABLE INERTIAL SWITCH FOR A PROJECTILE The present invention relates to inertial or impact switches and is particularly concerned with such switches especially adapted for use in connection with artillery ammunition.

Most artillery ammunition comprises an explosive projectile portion and quite a few of these projectile portions are arranged to explode upon contact. When explosion of a projectile on contact is desired, an inertial type switch mounted in the projectile is a convenient, satisfactory and expedient way of obtaining the desired results.

With such a projectile the usual arrangement is the combination of an explosive charge, a detonator for the explosive charge, an electrical device in the detonator for igniting the detonator upon energization of the electrical device, a source of electric power carried by the projectile and a normally open inertial type switch connected in series with the battery and the electrical device so that closing of the switch will ignite the detonator which will, in turn, ignite the explosive charge and bring about explosion of the projectile.

While inertial switches of the general nature referred to above are know, it has not heretofore been the case that such switches have been capable of any adjustment and it has been ascertained that adjustment of the conditions under which the switch will close is a desirable feature. For example, the conditions may be such that it can be depended upon that the projectile will make a substantially direct impact with the target object. Under these conditions, an inertial switch which closes only upon a high rate of deceleration of the projectile which carries it is quite satisfactory and reliable for obtaining explosion of the projectile.

There are other conditions, however, when the possibility of graze impact, oblique impact, and fairly light target impact conditions will be possibilities and some of which may be dictated by the particular tactical situations in the field. It is desirable design criterion, that a capability be made within the projectile which will make it possible to adjust the rate of deceleration of the projectile for operating the inertial impact switch of the projectile.

In an inertial or impact switch, the conditions of operation of the switch are determined by the following equation:

G=lg where:

From the foregoing equation it will be appreciated that the deceleration required for closure of the switch can be adjusted by adjusting any of the spring modulus, or the distance required to effect closing of the switch, or the mass which is effective for overcoming the spring to close the switch.

Having the foregoing in mind is a primary object of the present invention to provide an inertial or impact switch especially adapted for use with artillery projectiles in which the amount of deceleration of the projectile required to close the switch can readily be adjusted.

Another object of this invention is to provide an adjustable inertial or impactswitch for use with artillery projectiles in which the closing conditions of the switch can be adjusted after it is mounted on the projectile.

Still a further object of this invention is a provision of an inertial or impact switch which is especially adaptedfor use with an artillery projectile which can readily be adjusted in the field so that the particular tactical situation at the time the projectile is to be fired can be taken into account.

A still further object of this invention is the provision of an inertial or impact switch as referred to above which is capable of a wide range of adjustment.

Still another object of this invention is a provision of an inertial or impact switch of the general nature referred to above which is simple and inexpensive and which can be adjusted with relative certainty to meet the particular tactical situation existing.

The foregoing objects of the present invention, as well as still other objects and advantages thereof will become more apparent upon reference to the accompanying drawings in which:

FIG. I is a fragmentary view of the nose end of an artillery projectile showing an adjustable inertial or impact switch arrangement according to the present invention mounted therein;

FIG. 2 is a vertical sectional view indicated by line II-II on FIG. [and drawn at somewhat enlarged scale;

FIG. 3 is a fragmentary view showing a modification;

FIG. 4 is a sectional view showing another type of inertial or impact switch according to the present invention;

FIG. 5 is a vertical sectional view indicated by line VV on FIG. 4;

FIG. 6 is a vertical sectional view showing another form of an inertial or impact switch according to the present invention; and

FIG. 7 is a sectional view indicated by line VII-VII on FIG.

Referring to the drawings somewhat more in detail, FIG. 1 illustrates the nose end of a projectile and which nose end may comprise a metal body portion 10 having a block 1 l of insulating material thereon. Block 11 has a cavity 12 therein in which is mounted an electrical power pack or battery 14. Battery 14 has a wire 18 connected to one terminal thereof and which wire leads to one terminal of the electrical igniting device of a detonator 20. The other terminal of the igniting device of the detonator is connected by a wire I6 with the metal shroud member 22 which forms the inwardly tapering nose end of the projectile.

Another metal body 24 is mounted in a counterbore in the outer end of recess 12 in electrical insulating member 11 and is retained therein by nut 26.

Member 24 is of electrically conductive material and is in contact with the other terminal of battery or power pack 14 at 28.

The outer tip end of member 24 has a tenon thereon on which is mounted a sleeve 30 of electrical insulating material. At the outer end of sleeve 30 is a first electrically conductive contact element 32 which is retained in place by the turned in edge portion 34 of shroud member 2.2. Contact element 32 is in electrical contact with shroud member 22, via the turned edge portion of edge 34.

The outer tip end of member 24 has a bore 36 therein in which is reciprocally mounted a pin 38 of electrically conductive material and forming a second and movable contact element. Pin 38 has a head 40 at its inner end and between the upper side of head 40 and the under side of a retainer plate 42 is a compression spring 44. Plate 42 may be in the form of a snap ring or may otherwise be suitably retained near the mouth end of recess 36 and is centrally apertured so that pin 38 can pass freely therethrough into position to contact the contact element 32.

It will be apparent that the mass of pin 38 taken together with the modulus of spring 44 and the distance between the outer tip of pin 38 and contact element 32 will determine the degree of deceleration of the projectile required to cause the pin 38 to advance forwardly against the resistance of spring 44 into position to contact the contact element 32. It will also be evident that pin 38 is electrically common with member 24 so that when pin 38 closes on contact element 32 the circuit will be completed to the electrical firing device in the detonator 20.

According to the present invention member 24 has a cylindrical bore 46 therein immediately rearwardly of the inner end of pin 38. The bore 36 in which pin 38 is reciprocally mounted advantageously opens directly into bore 46. Within bore 46 is a cylindrical selector element 48 which may be retained in position by a retainer ring 50 and which element 48 comprises a head portion 52 by means of which the element may be rotated in bore 46.

Cylindrical element 48, as will be seen in FIGS. 1 and 2, has a first bore 54 extending diametrally therethrough and this bore is counterbored from one side of cylindrical element 48 by a counterbore 56. A sleeve 58 is disposed in counterbore 56 and a pin 60 extends completely through bore 54 and the central bore in sleeve 58. At this point it will be apparent that the mass of pin 38 can be selectively augmented by the mass of pin 60 or by the mass of pin 60 taken together with the mass of sleeve 58 by positioning the cylindrical selector member 48 in predetermined rotated positions. For example, in the position in which the cylindrical selector member is illustrated in FIGS. 1 and 2, pin 38 has its mass augmented by the mass of both pin 60 and sleeve 58 and this added mass will materially decrease the rate of deceleration of the projectile necessary to cause pin 38 to move into electrical contacting engagement with contact 32.

Alternatively, the cylindrical selector member can be rotated 180 from the position in which it is illustrated, in which case the mass of pin 38 will be augmented by the mass of pin 60 only. In still a third position of cylindrical selector member 48, in which the axis of pin 60 is offset from the axis of pin 38, neither the pin 60 nor the sleeve 58 will be effective for augmenting the mass of pin 38. The arrangement illus trated in FIGS. 1 and 2 thus shows an arrangement wherein three effective masses are available for actuating the switch into closed position so that three different operational conditions can be met.

FIG. 3 shows how a cylindrical selector element 70 could be provided, positioned immediately behind a primary mass element 72, with the selector member 70 being provided with bores 74, 76, 78, and 80 each opening radially outwardly and each containing a respective and different sized mass element 82, 84, 86, and 88. It will be evident with the arrangement of FIG. 3, an intermediate setting of cylindrical selector element 88 will provide for the mass closing the switch whereas in each of four different effective positions of selector member 88 a single one of the mass elements 83, 84, 86, and 88 will be effective for providing for a different total mass for actuating the switch toward closed position.

At this point it is to be noted that while the varying degrees of mass of the elements indicated in FIG. 3 is obtained by making the elements of different size, it is also possible to obtain different degrees of mass by selecting elements of the same size but of differing specific gravity. For instance, a relatively light element could be formed of a magnesium bearing material, a somewhat heavier element from an aluminum bearing material, a still heavier element from steel or brass, and a still heavier element could be made from a tungsten bearing material. All of these elements could be made the same size but would have substantially different effective masses.

Turning now to FIGS. 4 and 5, in the arrangement shown therein there is a first stationery but adjustable contact element 90 and a second movable contact element 92 which is in the form of a pin movable axially toward contact element 90. A spring 94 restrains pin 92 from movement except under predetermined axial force. Pin 92 is reciprocal in a bore 96 in a metal member 98 and is retained in place by a cap 100. A spring 94 bears between the underside of cap 100 and the upper side of the head of pin 92.

The body 98 is contained within an electrical insulating sleeve 102 and mounted on sleeve 102 is a metal cap 104. Metal cap 104 is traversed by shaft-like member 106 which has an adjusting portion 108 on one end and which may have its other end frictionally retained as by the Belleville spring 110.

The contact element 90 is in the form of a disc-like member having an inclined surface on one side at 112 which extends of pin 72 only to be effective for g across the path of movement of movable contact element 92. It will be evident that rotation of contact element will be ef fective for adjusting the amount of movement required for movable contact element 92 to move from its rest position into the position where it contacts contact element 90. Advantageously, in order to provide for the maximum degree of adjustability of the switch illustrated, haft-like member 106 is laterally offset from the path of movable contact element 92, as shown in FIG. 5, so that it is a portion of surface 112 radially spaced from the shaftlike member which lies in the path of movement of movable contact element 92.

In the arrangement illustrated in FIGS. 4 and 5, the parameter which is changed in the equation given in the beginning of the specification isthe distance x and increase of this distance will increase the rate of deceleration of the projectile which is required to close the inertial switch whereas decreasing the said distance will decrease the rate of deceleration of the projectile which is required to close the inertial switch.

FIG. 6 and 7 show a modification wherein, as before, the movable contact element is in the form of a pin 120, movement of which, under deceleration of the projectile, is restrained by a spring 122. A stationery but adjustable contact is provided in the space ahead of pin 122 and takes the form of a substantially cylindrical body 124 having a peripheral groove 126 therein which, as will be noted in FIG. 7, is of varying depth. When the projectile is decelerated, and pin 102 advances, the switch will be closed when the pin contacts the bottom wall of groove 126. By rotating the member 124 this distance can readily be varied from a predetermined maximum to a predetermined minimum. Member 124 is mounted upon a shaft 128 which extends transversely through the structure and which comprises a head portion 130 by means of which the shaft and the member 124 mounted thereon can be angularly adjusted.

In FIGS. 4 and 5, the selector means takes the form of a shaft and a knob or slotted head for rotating the shaft and the contact element thereon. In FIGS. 1 through 3 the stationery contact element is not adjustable and the selector member is in the form of a cylindrical member carrying mass elements made to be selectively effective by rotation of the selector member.

In the various switches shown, crushing of the nose of the projectile may be effective for closing the switch and this will be particularly noted in FIGS. 6 and 7. The structure supporting contact element or grazing impact, the relatively thin outer member in which shaft 128 is rotatably mounted will bend or deflect and member 124 will readily make contact either with the outer end of pin 120 or with the metal plate 142 which retains the spring 122 and pin 120 in the recess provided therefore in metal member 144. Such contact between element 124, and pin 120 or cover 142, will complete the circuit from the power pack 146 through the electric ignitor for the detonator.

By suitable modification of the structure, a contact plate 148 could be mounted in the extreme nose of the projectile and make electrical contact with contact element 124 upon bending or crushing of the nose end of shroud member 140 due to a glancing or grazing contact. It will be understood that, in this last mentioned case, plate 148 and contact element 124 would be electrically isolated from each other and so connected in the circuit to the electrical ignitor device that closing of these elements on each other would complete the circuit and ignite the the detonator.

It will be noted in FIG. 7 that the bottom wall 150 of the groove 126 in member 124 is in the form of a pair of archimedean spirals and this form of groove is illustrated because it permits straight line calibration of a scale which might be inscribed either on shroud member 140 about the recess in'which head 130 of shaft 128 is located, or might be inscribed directly on the head 130 of the shaft and be read against a gauge mark on shroud member 140. In the switch of FIG. 7, and which might be used as an example as to the range of adjustability of all of the switches, if the minimum distance 124 is so arranged that, upon a glancing between the outer end of pin 120 and contact member 124 is such that it requires a deceleration of the projectile on the order of 20 6'5 for closing of the switch, the maximum distance which the pin 120 must move might require deceleration on the order of 200 G5 for closure of the switch. lt will be apparent that this range could be made wider if necessary or, if conditions permitted, the range could be substantially narrower.

In any case, an inertial switch is shown, particularly for use with an electric fuse for an artillery projectile, which switch is adapted for closing upon impact of the projectile with a target object and wherein the conditions of deceleration under which the switch will close can readily be adjusted even up to just before firing of the projectile so that varying tactical situations can be met in the field.

It will be apparent that it would be a simple matter to so balance all of the rotatable elements of the inertial switch structure that the initial acceleration of the projectile from the gun in which it is fired would not disturb the setting of any of these members. It will also be evident that the illustrations in the drawings are somewhat diagrammatic and that the switch arrangement of the present invention could be arranged so that there were no protruding portions or holes or surface irregularities that would tend to create undesirable air resistance conditions on the projectile when the projectile was in flight.

We claim:

1. An inertial switch adapted for use with an electrically operated detonator for an explosive artillery projectile; said switch comprising first and second electrical contacts adapted for being carried by the projectile, said contacts being spaced and in electrically isolated relation and being movable relatively into contacting postion to complete a circuit operable to ignite the detonator of the projectile, spring means resisting movement of said contacts relatively toward contacting position, mass means movably carried by said projectile and operatively connected to said contacts so that movements of said mass means will cause relative movement of said contacts, said mass means being sensitive to deceleration of said projectile to tend to move in a direction to cause said contacts to close on each other against the resistance of said spring means, and selector means for adjusting at least one of the spacing between said contacts and the effective amount of said mass means and the effective modulus of said spring means to vary the rate of deceleration of the projectile required to cause said contacts to move under the influence of said mass means and against the resistance of said spring means into contacting position.

2. An inertial switch according to claim 1 in which said selector means is operable for adjusting the effective amount of said mass means only.

3. An inertial switch according to claim 1 in which said selector means is operable for adjusting the spacing between said contacts only.

4. An inertial switch according to claim 2 in which said mass means comprises a first mass element movable in the direction of flight of the projectile upon deceleration of the projectile and at least one other mass element located directly behind said first mass element and connected to said selector means and movable by said selector means from an effective position where said other mass element engages said first mass element and acts jointly therewith during deceleration of the projectile to an ineffective position where said other mass element does not engage said first mass element and said first mass element is singly effective during deceleration of the projectile.

5. An inertial switch according to claim 2 in which said mass means comprises a first mass element movable in the direction of flight of the projectile upon deceleration of the projectile and at least two other mass elements located directly behind said first mass element, said selector means comprising a cylindrical member directly behind said first mass element and comprising radial bore means in which said other mass elements are dis osed for radial movability, said selector means being rotatab e to position a selected one of said other mass elements in axial alignment with said first mass element to act jointly therewith during deceleration of said projectile, said selector means also being rotatable to position all of said other mass elements out of axial alignment with said first mass element whereby said first mass element is singly effective during deceleration of the projectile.

6. An inertial switch according to claim 3 in which said contacts comprises a first stationery but adjustable contact and a second movable contact, said second contact having a predetermined rest position and being movable toward said first contact by said mass means upon deceleration of said projectile, said first contact being supported by said selector means and being movable thereby to vary the distance the second contact moves from its rest position to the position where it engages said first contact.

7. An inertial switch according to claim 6 in which said second contact is a pin-like element, the path of movement of 4 which is in the axial direction when actuated by said mass means upon deceleration of said projectile, said selector means being located forwardly of said second contact and comprising a rotatable shaft-like member offset laterally from the path of movement of said second contact, said first contact being mounted on said shaft-like member so as to be rotated thereby and having one face radially spaced from said shaftlike member and which face is in the form of an inclined surface which intersects the path of movement of said second contact whereby angular adjustment of said first contact by rotation of said selector means will vary the amount of movement of said second contact from its rest position to the position where it engages said first contact.

8. An inertial switch according to claim 6 in which said second contact is a pin-like element the path of movement of which is the axial direction when actuated by said mass means upon deceleration of said projectile, said selector means being located forwardly of said second contact and comprising a rotatable shaft-like member offset laterally from the path of movement of said second contact said first contact comprising a drum-like member mounted on said shaft-like member, and a circumferential groove in said drum-like member in the path of movement of said second contact and varying in depth whereby angular adjustment of said first contact by rotation of said selector means will vary the amount of movement of said second contact from its rest position to the position where it engages said first ontact.

9. An inertial switch according to claim I which includes a support body for said switch at the nose end of the projectile, said support body being collapsable upon the exertion of a lateral force thereon such as would occur from oblique impact of the projectile with a target object,said contacts engaging upon collapse of said body to cause ignition of the detonator connected thereto.

10. An inertial switch according to claim 1 which includes a source of electrical power carried by the projectile, an electrically ignitable detonator carried by the projectile, said source of electrical power and said detonator and said contacts being connected in series. 

